1. Field of Invention
The invention relates to a power management system.
2. Related Art
The biggest problem caused by the vehicles or generators using the fossil fuel, such as gasoline or diesel fuel, is to produce the air pollution. Thus, with the rising environmental awareness, utilizing the battery as the power source for the vehicles or generators to have a lower pollution has become a major development direction in the industry. The vehicles and the other large-scale machines require higher voltage and current during operation, and are mostly driven by Alternating-Current (AC) power sources or even a multi-phase AC power source. So, when using the battery as the power supply unit, multiple batteries are usually connected in series and/or parallel to increase the output voltage and/or current of the power supply unit, and the power supply output are converted into an AC power or even a multi-phase AC power.
Due to the characteristics of the battery, such as the residual capacity and the like, the matching conditions of the batteries must be considered when multiple batteries are serially connected for operation. If the batteries are serially connected when in charging, the batteries with higher residual capacities could be damaged by overcharging, and the batteries with lower residual capacities will probably be not fully charged. During the discharging operation, a battery could be damaged by over-discharging due to the differences of the characteristics and the different residual capacities between the batteries.
Therefore, it is an important subject to provide a power management system which can adjust the connection configuration of the power units in accordance with the requirements of the charging voltage, the desired output voltage, or the state of each battery module, so that the power units can be charged with an AC power, or can output an AC power or a multi-phase AC power, and can be effectively protected and/or balanced during charging/discharging, and avoid from being damaged.